Vitamin D, also known as the “sunshine vitamin,” is a largely under-appreciated prohormone, mostly known for supporting bone health by promoting the absorption of vitamin C and phosphorus in the body. But in the last decade, scientists have come to believe that vitamin D actually does much more.
Recent research suggests vitamin D may play an important role in the prevention of one of the leading causes of death in women worldwide – breast cancer.
Vitamin D and Breast Cancer Prevention
Epidemiological research has shown that incidence rates of breast cancer are lower among women with higher levels of vitamin D in their blood. It is estimated that there is a 30 to 50% reduction in risk for developing breast cancer for women who increase their vitamin D intake to 1,000 International Units (IUs) per day. A study of 1,200 premenopausal women found that women with the lowest levels of vitamin D in their blood three months before breast cancer diagnosis had three times the risk of breast cancer as the women with the highest levels of vitamin D.1
RELATED: Vitamin D: Is Sunlight Enough?
There are also noticeable relationships between factors that lead to lower vitamin D levels and breast cancer rates. Vitamin D levels are determined by numerous variables including latitude of residence, skin color, and exposure to the sun. Women who get more vitamin D in their diets or who spend more time outdoors are 25 to 45% less likely to develop breast cancer than women who don’t.2
Researchers are finding that women who get little exposure to sunlight, reside in northern latitudes, or whose customs require them to cover most of their bodies are all at higher risk for breast cancer. What’s the common factor among them all? Vitamin D. According to Michael F Holick, head of the Vitamin D, Skin, and Bone Research Laboratory at the Boston University School of Medicine, activated vitamin D is one of the most potent inhibitors of cancer cell growth.3
“Women who get more vitamin D in their diets or who spend more time outdoors are 25 to 45% less likely to develop breast cancer than women who don’t.”
Increased Cancer Survival Rates
Not only may vitamin D help prevent breast cancer, but vitamin D is also strongly associated with breast cancer survival.4 In fact, high levels of vitamin D may halve breast cancer fatality. Dr. Cedric Garland, of the University of California, San Diego School of Medicine, conducted a meta-analysis of five studies with 4,443 female patients that examined the link between breast cancer and vitamin D.
The participants in the studies were divided into groups based on the levels of vitamin D in their blood and were followed for nine years. The research team found the women with higher levels of vitamin D in their blood had a staggering 50% lower fatality rate than the women with lower levels of vitamin D in their blood.5
How Does Vitamin D Prevent Cancer?
Vitamin D plays an important role in intercellular communication, which ensures healthy cell reproduction. One of the first events with cancer is loss of communication between cells. This shortcoming in the exchange of information between cells prevents the turnover of healthy cells, allowing more aggressive cancer cells to take over.
“More than one billion people worldwide are vitamin D deficient.”
Lab studies on mice have shed light on other vitamin D activities that may cause prevention or slowing of cancer development. Some of these activities include decreasing cancer cell growth, the stimulation of cell death, reduction in tumor blood vessel formation, and promotion of cellular differentiation.6
The Danger of Vitamin D Deficiency
With its cancer-fighting, bone-supporting, and immune-boosting capabilities, vitamin D is looking like a superhero hormone. Yet, vitamin D deficiency is a worldwide pandemic. The Institute of Medicine recommends that people up to the age of seventy get 200 to 600 IUs of vitamin D daily. But approximately 75% of U.S. teens and adults are not reaching these marks.7More than one billion people worldwide are vitamin D deficient.8
One of the main reasons vitamin D deficiency is so common is that we aren’t spending enough time under the sun. The greatest source of vitamin D for most people is exposure to sunlight. Vitamin D is actually the only vitamin that our bodies are able to manufacture, and it does so with sun exposure. But because we put on sunscreen when outdoors and most of us don’t live in a climate where it’s beach weather year round, many people don’t spend adequate time, unprotected, under the sun.
There also aren’t many natural dietary sources of vitamin D. You can find vitamin D in fatty fish like salmon, mackerel, or tuna. There are also small amounts of vitamin D in cheese, beef liver, and egg yolks. Everyday foods like orange juice, milk, and yogurt are frequently fortified with vitamin D in the United States. But if you don’t eat enough of these foods or don’t expose yourself to sunlight on a daily basis, look to a dietary supplement to meet your vitamin D needs.
The Bottom Line on Vitamin D and Breast Cancer
Approximately one in eight women in the United States will develop breast cancer in the course of her lifetime.9 While the research regarding vitamin D and breast cancer is relatively preliminary, there is intriguing evidence of substantial cancer-combatting capabilities. So, get more vitamin D. And belated Happy Vitamin D Day (November 2)!
1. “Low Vitamin D Levels Linked to High Risk of Premenopausal Breast Cancer.” UC San Diego Health System. January 24, 2013. Accessed November 2, 2014.
2. “Higher Vitamin D May Help Prevent Breast Cancer.” Harvard Health Publications. Accessed October 12, 2014.
3. Chang, L. “Benefits of Vitamin D – WebMD.” WebMD. Accessed October 5, 2014lol
4.Kim, Y., and Je, Y. “Vitamin D Intake, Blood 25(OH)D Levels, and Breast Cancer Risk or Mortality: A Meta-analysis.” British Journal of Cancer. May 27, 2014. Accessed November 1, 2014.
5. Whiteman, H., “High Vitamin D Levels May Increase Breast Cancer Survival.” MNT. March 17, 2014. Accessed November 2, 2014.
6. “Vitamin D and Cancer Prevention.” National Cancer Institute. Accessed November 2, 2014.
7. Lite, J. “Vitamin D Deficiency Soars in the U.S., Study Says.” Scientific American Global RSS. March 23, 2009. Accessed November 2, 2014.
8. “Information on the Latest Vitamin D News and Research.” Vitamin D Council. Accessed November 3, 2014.
9. “U.S. Breast Cancer Statistics.” Breastcancer.org, 20 Sept. 2014. Web. 3 Nov. 2014.
Photos courtesy of Shutterstock.